The invention relates to a facility for the contact-free disintegration of a calculus located in the body of a living being and comprising a shock wave generator which can be directed to a target region in the body.
Facilities of this type are employed in medicine, for example for the pulverization of stones in the kidney of a human being. They are particularly advantageous because they avoid any and all surgical intervention in the body. It is not necessary to proceed surgically. The application of probes and devices to the calculus is likewise eliminated. A hazard due to infections or injuries, for example upon introduction of the probe or given surgical operations, cannot occur in the case of contact-free pulverization.
A facility of the type initially mentioned is disclosed in the German AS 23 51 247 (U.S. Pat. No. 3,942,531). Herein, a spark discharge is initiated between two electrodes at a first focus in a focussing chamber that is designed as a hemispherical ellipsoid of revolution. Said spark discharge causes a shock wave whose wave front propagates at all directions, i.e. spherically. The waves are reflected at the wall of the ellipsoid of revolution. They collect at the second focus of the elliptical reflector. The reflected waves arrive simultaneously at the second focus at which the calculus is located. The calculus is shattered under the focussed impact of the shock waves. The coupling between the one ellipsoid half and the body in which the calculus is located occurs via a thin film which presses against the body free of an air gap. The focussing chamber is filled with water.
This facility involves the disadvantage that changes in the shock wave energy are only possible within narrow limits and only with a considerable apparatus outlay by means of changing the spacing of the underwater electrodes. It is further disadvantageous that the mutual spacing of the electrodes must usually amount to a number of millimeters in order to generate high-intensity shock waves, the shock wave source therefore not having a punctiform geometry and imaging errors therefore possibly occurring in the focussing. Further, the underwater electrodes wear greatly with every discharge, so that their service life is limited, this requiring regular servicing of the facilities.